December 6th

Hummingbird metabolism is a marvel of evolutionary engineering. These tiny birds can power all of their energetic hovering flight by burning the sugar contained in the floral nectar of their diet. Now new research from the University of Toronto Scarborough (UTSC) shows these tiny birds are equally adept at burning both glucose and fructose, which are the individual components of sucrose; a unique trait other vertebrates cannot achieve. "Hummingbirds have an optimal fuel-use strategy that powers their high-energy lifestyle, maximizes fat storage, and minimizes unnecessary weight gain all at the same time," says Dr. Kenneth Welch, assistant professor of biological sciences at UTSC and an expert on hummingbirds. Dr. Welch and his graduate student Chris Chen, who is co-author of the research article, fed hummingbirds separate enriched solutions of glucose and fructose while collecting exhaled breath samples. The researchers found that the birds were able to switch from burning glucose to fructose with equal facility. "What's very surprising is that, unlike mammals such as humans, who can't rely on fructose to power much of their exercise metabolism, hummingbirds use it very well. In fact, they are very happy using it and can use it just as well as glucose," says Dr. Welch. Hummingbirds require an incredible amount of energy to flap their wings 50 times or more per second in order to maintain hovering flight. In fact, if a hummingbird were the size of a human, it would consume energy at a rate more than 10 times that of an Olympic marathon runner. They are able to accomplish this by burning only the most recently ingested sugar in their muscles while avoiding the energetic expenditure of first converting sugar into fat.

December 5th

Dr. Gerald Zon’s latest “Zone in with Zon” blog post, dated December 2, 2013, and published by TriLink BioTechnologies of San Diego, provides a fascinating discussion of the developing use of modified mRNAs in a wide variety of key applications, including gene therapy, nucleic acid vaccines, and cellular reprogramming, as well as the possibly tremendous commercial potential of modified mRNA technology in these and other areas. Dr. Zon begins by discussing the intellectual simplicity of gene therapy, i.e., to simply replace a broken gene with the DNA of the normal gene and thus ultimately generate the normal version of the missing or altered protein. Unfortunately, it has proven remarkably difficult over three decades of work to achieve this effectively and safely. Dr. Zon attributes this in part to the challenges for cell- or tissue-specific delivery, as well as concern for adverse events generally ascribed to unintended vector integration leading to neoplasias. Nevertheless, there are presently more than 1700 clinical trials of gene therapy taking place around the world. However, as a consequence of the slow progress of DNA-based gene therapy, a number of researchers have recently turned to the study of modified mRNAs that might be used to produce the missing protein directly by translation. This field is called “mRNA therapeutics.” Another application is in the use of mRNAs as cancer vacccines. Here the idea is to use mRNAs coding for tumor-associated antigens to induce specific immune responses to the tumor. Dr. Zon notes that a 2013 review from Novartis Vaccines & Diagnostics, and entitled “RNA: the New Revolution in Nucleic Acid Vaccines,” claims that the “prospects for success are bright.” The reasons for this, Dr.